Sperm counts may be declining globally, review finds, adding to debate over male fertility

 

Over the past 50 years, human sperm counts appear to have fallen by more than 50% around the globe, according to an updated review of medical literature.
If the findings are confirmed and the decline continues, it could have important implications for human reproduction. Researchers say it would also be a harbinger of declining health in men in general, since semen quality can be an important marker of overall health.
The review, and its conclusions, have sparked a debate among experts in male fertility. Some say the findings are real and urgent, but others say they are not convinced by the data because the methods of counting sperm have changed so much over time that it’s not possible to compare historical and modern numbers.Nearly all experts agree that the issue needs more study.
“I think one of the fundamental functions of any species is reproduction. So I think if there is a signal that reproduction is in decline, I think that’s a very important finding,” said Dr. Michael Eisenberg, a urologist with Stanford Medicine who was not involved in the review.
“There is a strong link between a man’s reproductive health and his overall health. So it could also speak to that too, that maybe we’re not as healthy as we once were,” he said.
Others say that while the review was well-done, they are skeptical about its conclusions.
“The way that semen analysis is done has changed over the decades. It has improved. It has become more standardized, but not perfectly,” said Dr. Alexander Pastuczak, a surgeon and assistant professor the University of Utah School of Medicine in Salt Lake City. He was not involved in the review.
“Even if you were to take the same semen sample and run it and do a semen analysis on it in the 1960s and ’70s versus today, you’d get two different answers,” he said.
Pastuczak says that in more contemporary studies of semen analysis, ones that rely on samples analyzed by a different method, “you don’t see these trends.” In fact, some studies in Northern European regions show sperm counts going up over time, not down, he said.